AB1042 PATIENT CHARACTERISTICS AND SPA FEATURES IN RECENTLY DIAGNOSED AXIAL SPONDYLOARTHRITIS PATIENTS STRATIFIED FOR CLINICAL DIAGNOSIS AND ASAS CLASSIFICATION CRITERIA; RESULTS FROM STANDARD-OF-CARE COHORT
Authors: J. M. Nijmeijer, S. Kieskamp, F. Wink, S. Arends, A. Spoorenberg
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In axial spondyloarthritis (axSpA), besides the characteristic symptoms of chronic (inflammatory) back pain and stiffness, patients may suffer from peripheral and extra-skeletal manifestations. Within axSpA, patients can be diagnosed with ankylosing spondylitis (AS) or non-radiographic axSpA (nr-axSpA) based upon the presence or absence of radiographic sacroiliitis. Furthermore, patients can be classified as axSpA according to the ASAS criteria into the imaging arm for which radiographic sacroiilitis and/or sacroiliitis on MRI is mandatory or into the clinical arm for which the presence of HLA-B27 is mandatory. Until now, little is known about patient characteristics in these subgroups of axSpA with a recent axSpA diagnosis. <h3>Objectives</h3> To explore patient characteristics and SpA features in recently diagnosed axSpA patients diagnosed as AS or nr-axSpA and in patients fulfilling the imaging or clinical arm of the ASAS classification criteria. <h3>Methods</h3> This cross-sectional analysis included consecutive axSpA patients between 2009 and 2019 diagnosed no more than 1 year before inclusion in the Groningen Leeuwarden Axial Spondyloarthritis (GLAS) cohort. Demographic data and all SpA features based on the ASAS classification criteria (sacroiliitis on pelvic radiograph according to the modified New York criteria, sacroiliitis on MRI according to the ASAS criteria, inflammatory back pain (IBP) according to the ASAS criteria; peripheral manifestations (peripheral arthritis, enthesitis and dactylitis); extra-skeletal manifestations (uveitis, psoriasis, inflammatory bowel disease); good response to a NSAID; family history of SpA; HLA-B27 status and CRP level) were collected at the GLAS baseline visits. Characteristics and features of the following axSpA subgroups were analyzed: clinical diagnosis AS vs. nr-axSpA, imaging arm vs. clinical arm of the ASAS classification criteria, only axial disease vs. axSpA with ≥1 peripheral manifestation. <h3>Results</h3> In total, 319 aSpA patients were included, with a mean age of 38.2 ± 12.0 years, 175 (55%) were male, median symptom duration was 25 (19-34) years and 242 (76%) were HLA-B27 positive. 177 (55%) patients were diagnosed with AS and 142 (45%) with nr-axial SpA. AS patients were more often male (65% vs. 42%, p&lt;0.001), had more often IBP (89% vs. 76%, p=0.004), more often a SpA family history (38% vs 22%, p=0.002) and higher CRP (median 5 vs. 2, p=0.001) compared to patients diagnosed with nr-axSpA. The number of SpA features was not significantly different between patients diagnosed with AS or nr-axSpA (median 3.7 vs. 3.7, p=0.73). 265 (83%) axSpA patients fulfilled the imaging arm and 54 (17%) patients fulfilled the clinical arm. Patients fulfilling the clinical arm were per definition all HLA-B27 positive (100% vs. 71%, p&lt;0.001), had more often IBP (92% vs. 80%, p=0.040) and a positive SpA family history (51% vs. 25%, p&lt;0.001) compared to patients fulfilling the imaging arm. Furthermore, patients from the clinical arm showed a higher CRP (median 4 vs. 2, p=0.028) and had more SpA features (median 4.1 vs. 3.6, p=0.019). 200 (64%) axSpA patients had only axial involvement without peripheral manifestations and 111 (36%) axSpA patients had ≥1 peripheral manifestations, of which 69% had a history of peripheral arthritis, 37% enthesitis and 17% dactylitis. Accordingly, axSpA patients with peripheral manifestations presented significantly more SpA features than patients with only axial involvement (median 4.5 vs. 3.2, p&lt;0.001). <h3>Conclusion</h3> In this large cross-sectional study of recently diagnosed (&lt;1 year) axSpA patients, the presence of IBP, positive family history and higher CRP occurred significantly more often in patients diagnosed with AS compared to patients diagnosed with nr-axSpA and in patients fulfilling the clinical arm compared to patients fulfilling the imaging arm of the ASAS classification criteria. <h3>References</h3> None. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.